Strongly Correlated Photons in a Photonic Crystal

Propagation of Light in Photonic Crystal Fibre Devices

We describe a semi-analytical approach for three-dimensional analysis of photonic crystal fibre devices. The approach relies on modal transmission-line theory. We offer two examples illustrating the utilization of this approach in photonic crystal fibres: the verification of the coupling action in a photonic crystal fibre coupler and the modal reflectivity in a photonic crystal fibre distributed Bragg reflector.

Kossel diffraction and photonic modes in one-dimensional photonic crystal

Kossel diffraction under standing-wave excitation in a one-dimensional photonic crystal is investigated. It is shown that by combining the reciprocity theorem, the Fermi golden rule and the concept of density of photonic modes, it is possible to predict the behaviour of the Kossel diffraction in such a system.

Photonic and plasmonic guiding modes in graphene-silicon photonic crystals

We report systematic studies of plasmonic and photonic guiding modes in large-area chemical-vapor-deposition-grown graphene on nanostructured silicon substrates. Light interaction in graphene with substrate photonic crystals can be classified into four distinct regimes depending on the photonic crystal lattice constant and the various modal wavelengths (i.e. plasmonic, photonic and free-space). By optimizing the design of the substrate, these resonant modes can magnify the graphene absorption in infrared wavelength, for efficient modulators, filters, sensors and photodetectors on silicon photo…

Photonic density of states maps for design of photonic crystal devices

In this work, it has been investigated whether photonic density of states maps can be applied to the design of photonic crystal-based devices. For this reason, comparison between photonic density of states maps and transmittance maps was carried out. Results of comparison show full correspondence between these characteristics. Photonic density of states maps appear to be preferable for the design of photonic crystal devices, than photonic band gap maps presented earlier and than transmittance maps shown in the paper.

Experimental demonstration of self-collimation beaming and splitting in photonic crystals

I studied experimentally the beam self-collimation and splitting in two-dimensional microwave photonic crystals. Using a microwave photonic crystal fabricated from alumina rods, I present an experimental proof of principle for an earlier theoretical proposal [A. Matthews et al., Opt. Commun. 279, 313 (2007)] of a photonic crystal beam splitter based on the self-collimation effect.

Simple model of the density of states in 1D photonic crystal

In this paper, we present a simple, yet versatile, analytical model of one-dimensional photonic crystal (1D PC). In our theoretical model, we take into account direction of propagation and therefore do not neglect anisotropic nature of photonic crystals. We derive analytical expressions for mode spectrum and density of states in 1D photonic crystal. With those formulas, we obtain mode spectrum characteristics, which depict formation of photonic band gap and reveal properties of photonic crystals.

Frequency-dependent topological phases and photonic detouring in valley photonic crystals

Here, the frequency degree of freedom is introduced into valley photonic crystals with dual band gaps. Based on the high-order plane wave expansion model, we derive an effective Hamiltonian which characterizes dual band gaps. Metallic valley photonic crystals are demonstrated as examples in which all four topological phases are found. At the domain walls between topologically distinct valley photonic crystals, frequency-dependent edge states are demonstrated and a broadband photonic detouring is proposed. Our findings provide the guidance for designing the frequency-dependent property of topol…

Optical States in a 1-D Superlattice with Multiple Photonic Crystal Interfaces

Interface states in a 1-D photonic crystal heterostructure with multiple interfaces are examined. It is found that the behavior of the localized modes in the photonic band gaps is dependent on whether there is an even or odd number of photonic crystal interfaces in the heterostructure. With certain sequences of all dielectric photonic crystals, topological states are shown to split in two, whereas for other heterostructures they are shown to vanish. Additional resonant modes appear depending on how many crystals are in the heterostructure.

Compound structure one-dimensional photonic crystal

In this paper, we have proposed a new compound structure one-dimensional photonic crystal, which include series connection, parallel connection and positive and negative feedback compound structure photonic crystal. We have studied their transmission characteristics and obtained some new results, which should be help to design new type optical devices, such as optical amplifier, photonic crystal laser and so on.

Chromatic dispersion of liquid crystal infiltrated capillary tubes and photonic crystal fibers

We consider chromatic dispersion of capillary tubes and photonic crystal fibers infiltrated with liquid crystals. A perturbative scheme for inclusion of material dispersion of both liquid crystal and the surrounding waveguide material is derived. The method is used to calculate the chromatic dispersion at different temperatures.

Two-dimensional function photonic crystals

In this paper, we have firstly proposed two-dimensional function photonic crystals, which the dielectric constants of medium columns are the functions of space coordinates $\vec{r}$, it is different from the two-dimensional conventional photonic crystals constituting by the medium columns of dielectric constants are constants. We find the band gaps of two-dimensional function photonic crystals are different from the two-dimensional conventional photonic crystals, and when the functions form of dielectric constants are different, the band gaps structure should be changed, which can be designed …

Topology of photonic time-crystals

We introduce topological phases in Photonic Time-Crystals. Photonic Time-Crystals are materials in which the refractive index varies periodically and abruptly in time. When the refractive index changes abruptly, the light propagating in the material experiences time-refraction and time-reflection, analogous to refraction and reflection in photonic crystals. Interference between time-refracted and time-reflected waves gives rise to Floquet-Bloch states and dispersion bands, which are gapped in the momentum. We show that photonic time-crystals can be in a topologically non-trivial phase, and cal…

Study of transmission properties for waveguide bends by use of a circular photonic crystal

We study the transmission properties for the waveguide bends composed by a circular photonic crystal. Two types (Y and U type) of the waveguide bends utilizing the circular photonic crystal are studied. It has been shown, compared with the conventional photonic crystal waveguide bends, transmission properties for these bends can be significantly improved. Over a 6.4% bandwidth, less than 1-dB loss/bend are observed. U bent waveguide, i.e., $180^o$ bend, can be easily realized with low loss using the circular photonic crystal.

Local temperature control of photonic crystal devices via micron-scale electrical heaters

We demonstrate a method to locally control the temperature of photonic crystal devices via micron-scale electrical heaters. The method is used to control the resonant frequency of InAs quantum dots strongly coupled to GaAs photonic crystal resonators. This technique enables independent control of large ensembles of photonic devices located on the same chip at tuning speed as high as hundreds of kHz.

Extraordinary wavelength reduction in terahertz graphene-cladded photonic crystal slabs

Photonic crystal slabs have been widely used in nanophotonics for light confinement, dispersion engineering, nonlinearity enhancement, and other unusual effects arising from their structural periodicity. Sub-micron device sizes and mode volumes are routine for silicon-based photonic crystal slabs, however spectrally they are limited to operate in the near infrared. Here, we show that two single-layer graphene sheets allow silicon photonic crystal slabs with submicron periodicity to operate in the terahertz regime, with an extreme 100x wavelength reduction and excellent out-of-plane confinement…

Directional free-space coupling from photonic crystal waveguides

We present a general approach for coupling a specific mode in a planar photonic crystal (PC) waveguide to a desired free-space mode. We apply this approach to a W1 PC waveguide by introducing small index perturbations to selectively couple a particular transverse mode to an approximately Gaussian, slowly diverging free space mode. This "perturbative photonic crystal waveguide coupler" (PPCWC) enables efficient interconversion between selectable propagating photonic crystal and free space modes with minimal design perturbations.

High-Q impurity photon states bounded by a photonic-band-pseudogap in an optically-thick photonic-crystal slab

We show that, taking a two-dimensional photonic-crystal slab system as an example, surprisingly high quality factors (Q) over 10^5 are achievable, even in the absence of a rigorous photonic-band-gap. We find that the density of in-plane Bloch modes can be controlled by creating additional photon feedback from a finite-size photonic-crystal boundary that serves as a low-Q resonator. This mechanism enables significant reduction in the coupling strength between the bound state and the extended Bloch modes by more than a factor of 40.

Role of incoherent substrate reflections in photonic crystal spectroscopy

A method is presented for modelling the optical properties of a photonic crystal structure mounted on a substrate which is thick enough that the light reflected from the back is incoherent with reflections from the front. Transmission and reflection spectra are presented for the cases where the structure is a multilayer planar microcavity and an opal photonic crystal. The contributions from the incoherent reflections can be very large, and in the photonic crystal case, change the positions of the spectral peaks.

设计具有给定反射系数谱的一维光子晶体结构

Designing the structure of an one-dimensional photonic crystal with a given spectrum of the reflection coefficient

本文提出一种将任意给定反射谱展开为基本光子带隙并求和的一维光子晶体逆向设计方法，并通过实验制备简单反射谱实例验证其可行性。

Optimised photonic crystal waveguide for chiral light-matter interactions

We present slow-light photonic crystal waveguide designs that provide a $\times$8.6 improvement of the local density of optical states at a fully chiral point over previous designs.

Nonspreading Light Pulses in Photonic Crystals

We investigate propagation of light pulses in photonic crystals in the vicinity of the zero-diffraction point. We show that Gaussian pulses due to nonzero width of their spectrum spread weakly in space and time during the propagation. We also find the family of nonspreading pulses, propagating invariantly in the vicinity of the zero diffraction point of photonic crystals.

Non-Hermitian two-dimensional photonic crystal flat lens

In this paper, a non-Hermitian two-dimensional photonic crystal flat lens is proposed. The negative refraction of the second band of photonic crystal is utilized to realize super-resolution imaging of the point source. Based on the principles of non-Hermitian systems, a negative imaginary part is introduced into the imaging frequency, in which case the imaging intensity and resolution are improved. The results indicate that the non-Hermitian system provides a new method to improve the imaging performance of the photonic crystal lens.

Photonic bands and defect modes in metallo-dielectric photonic crystal slabs

Photonic components based on structured metallic elements show great potential for device applications where field enhancement and confinement of the radiation on a subwavelength scale is required. In this paper we report a detailed study of a prototypical metallo-dielectric photonic structure, where features well known in the world of dielectric photonic crystals, like band gaps and defect modes, are exported to the metallic counterpart, with interesting applications to infrared science and technology, as for instance in quantum well infrared photodetectors, narrow-band spectral filters, and …

Second Harmonic Generation in Photonic Crystal Cavities in (111)-Oriented GaAs

We demonstrate second harmonic generation at telecommunications wavelengths in L3 photonic crystal cavities in (111)-oriented GaAs. The second harmonic power from photonic crystal cavities fabricated in (111)-oriented GaAs is significantly increased compared to those fabricated in conventional (001)-oriented GaAs.

A new varied-time photonic crystals

In this paper, we have firstly proposed a new one-dimensional varied-time photonic crystals, i.e., the refractive indices of media $A$ and $B$ are the time functions. We consider the varied-time photonic crystals of refractive indices period variation and calculate the transmissivity and electronic field distribution with and without defect layer, which are different from the conventional photonic crystals, which transmissivity and electronic field distribution are static, but the varied-time photonic crystals transmissivity and electronic field distribution are dynamic. We have obtained some …

Gap solitons in spatiotemporal photonic crystals

We generalize the concept of nonlinear periodic structures to systems that show arbitrary spacetime variations of the refractive index. Nonlinear pulse propagation through these spatiotemporal photonic crystals can be described, for shallow nonstationary gratings, by coupled mode equations which are a generalization of the traditional equations used for stationary photonic crystals. Novel gap soliton solutions are found by solving a modified massive Thirring model. They represent the missing link between the gap solitons in static photonic crystals and resonance solitons found in dynamic grati…

具有任意光谱特征的光子晶体结构的创建

Creation of photonic crystal structures with arbitrary spectral features

提出一种构建具有任意预定反射光谱的光子晶体结构的方法，通过算法设计、数值模拟和实验样品验证，实现了光谱响应的精确控制。

Fractal Photonic Crystal Waveguides

We propose a new class of one-dimensional (1D) photonic waveguides: the fractal photonic crystal waveguides (FPCWs). These structures are photonic crystal waveguides (PCWs) etched with fratal distribution of grooves such as Cantor bars. The transmission properties of the FPCWs are investigated and compared with those of the conventional 1D PCWs. It is shown that the FPCW transmission spectrum has self-similarity properties associated with the fractal distribution of grooves. Furthermore, FPCWs exhibit sharp localized transmissions peaks that are approximately equidistant inside the photonic ba…

Surface EM waves on 1D Photonic Crystals

We study surface states of 1D photonic crystals using a semiclassical coupled wave theory. Both TE and TM modes are treated. We derive analytic approximations that clarify the systematics of the dispersion relations, and the roles of the various parameters defining the crystal.

Topological Edge States in Bichromatic Photonic Crystals

Bichromatic photonic crystal structures are based on the coexistence of two different periodicities in the dielectric constant profile. They are realized starting from a photonic crystal waveguide and modifying the lattice constant only in the waveguide region. In this work, we numerically investigate the spectral and topological properties of bichromatic structures. Our calculations demonstrate that they provide a photonic analog of the integer quantum Hall state, a well known example of a topological insulator. The nontrivial topology of the bandstructure is illustrated by the formation of s…

High-Q aluminum nitride photonic crystal nanobeam cavities

We demonstrate high optical quality factors in aluminum nitride (AlN) photonic crystal nanobeam cavities. Suspended AlN photonic crystal nanobeams are fabricated in sputter-deposited AlN-on-insulator substrates using a self-protecting release process. Employing one-dimensional photonic crystal cavities coupled to integrated optical circuits we measure quality factors up to 146,000. By varying the waveguide-cavity coupling gap, extinction ratios in excess of 15 dB are obtained. Our results open the door for integrated photonic bandgap structures made from a low loss, wide-transparency, nonlinea…

Controlling Interface States in 1D Photonic Crystals by tuning Bulk Geometric Phases

Interface states in photonic crystals usually require defects or surface/interface decorations. We show here that one can control interface states in 1D photonic crystals through the engineering of geometrical phase such that interface states can be guaranteed in even or odd, or in all photonic bandgaps. We verify experimentally the designed interface states in 1D multilayered photonic crystals fabricated by electron beam vapor deposition. We also obtain the geometrical phases by measuring the reflection phases at the bandgaps of the PCs and achieve good agreement with the theory. Our approach…

Dirac points in helically structured 1D photonic crystals

We reported about observation of Dirac points in a helically structured 1D photonic crystals, moreover, both as in the presence of longitudinal magnetic field as its absence. We obtained analytical formulas for Dirac points frequencies and the analytical dispersion relations for wave vectors.

Laterally confined photonic crystal surface emitting laser based on monolayer tungsten disulfide operating at room temperature

We report a photonic crystal surface emitting laser using monolayer tungsten disulfide as the gain medium. The cavity design utilizes a heterostructure in the photonic crystal lattice to provide lateral confinement for a high quality factor with a compact active region. Room temperature continuous wave lasing is realized after integrating monolayer tungsten disulfide flakes onto the silicon nitride photonic crystal on quartz substrate. Highly directional, near surface normal emission has also been experimentally demonstrated.

Edge states in self-complementary checkerboard photonic crystals: Zak phase, surface impedance and experimental verification

Edge states of photonic crystals have attracted much attention for the potential applications such as high transmission waveguide bends, spin dependent splitters and one-way photonic circuits. Here, we theoretically discuss and experimentally observe the deterministic edge states in checkerboard photonic crystals. Due to the self-complementarity of checkerboard photonic crystals, a common band gap is structurally protected between two photonic crystals with different unit cells. Deterministic edge states are found inside the common band gap by exploiting the Zak phase analysis and surface impe…

Combined photonic-plasmonic modes inside photonic crystal cavities

In this article, we present a numerical study of the optical properties of a metal nanowire interacting with a localized cavity in a two dimensional photonic crystal. The nature of the modes, their wavelength and width are investigated as a function of the particle radius. It is shown in particular that a particle with diameter about the lattice constant presents very narrow resonances corresponding to hybrid photonic-plasmonic modes, where increased lifetime is attributed to the decrease of the radiative losses by interaction with the photonic crystal. These results open interesting applicati…

Mesoscopic self-collimation and slow light in all-positive index layered photonic crystals

We demonstrate a mesoscopic self-collimation effect in photonic crystal superlattices consisting of a periodic set of all-positive index 2D photonic crystal and homogeneous layers. We develop an electromagnetic theory showing that diffraction-free beams are observed when the curvature of the optical dispersion relation is properly compensated for. This approach allows to combine slow light regime together with self-collimation in photonic crystal superlattices presenting an extremely low filling ratio in air.

Photonic crystal nanobeam lasers

Photonic crystal lasers operating at room temperature based on high Q/V nanobeam cavities have been demonstrated. We reported a large spontaneous emission factor (~0.97) by fitting the L-L curve with the rate equations.

Veselago lens by photonic hyper-crystals

An imaging system functioning as a Veselago lens has been proposed based on the novel concept of photonic "hyper-crystal" -- an artificial optical medium synthesizing the properties of hyperbolic materials and photonic crystals. This Veselago lens shows a nearly constant negative refractive index and substantially reduced image aberrations. It can find potential applications in photolithography and hot-spots detection of silicon-based integrated circuits.

Direct Wide-angle Measurement of Photonic Band- structure in a Three-dimensional Photonic Crystal using Infrared Fourier Imaging Spectroscopy

We propose a method to directly visualize the photonic band-structure of micron size photonic crystals using wide angle spectroscopy. By extending Fourier Imaging Spectroscopy sensitivity into the infrared range we have obtained accurate measurements of the band-structures along the high-symmetry directions (X-W-K-L-U) of polymeric three-dimensional rod-connected diamond photonic crystals. Our implementation also allows us to record single-wavelength reflectance far field patterns showing a very good agreement with simulations of the same designs. This technique is suitable for the characteriz…

Microwave measurements of the photonic bandgap in a two-dimensional photonic crystal slab

We have measured the photonic bandgap in the transmission of microwaves through a two-dimensional photonic crystal slab. The structure was constructed by cementing acrylic rods in a hexagonal closed-packed array to form rectangular stacks. We find a bandgap centered at approximately 11 GHz, whose depth, width and center frequency vary with the number of layers in the slab, angle of incidence and microwave polarization.

莫尔光子晶体：从织物到奇迹

Moiré Photonic Crystals: from Fabric to Magic

研究莫尔光子晶体的宏观与亚波长特性，揭示其独特的慢光模式及零群速特性。

Efficient input and output fiber coupling to a photonic crystal waveguide

The efficiency of evanescent coupling between a silica optical fiber taper and a silicon photonic crystal waveguide is studied. A high reflectivity mirror on the end of the photonic crystal waveguide is used to recollect, in the backwards propagating fiber mode, the optical power that is initially coupled into the photonic crystal waveguide. An outcoupled power in the backward propagating fiber mode of 88% of the input power is measured, corresponding to a lower bound on the coupler efficiency of 94%.

Observation of soliton pulse compression in photonic crystal waveguides

We demonstrate soliton-effect pulse compression in mm-long photonic crystal waveguides resulting from strong anomalous dispersion and self-phase modulation. Compression from 3ps to 580fs, at low pulse energies(~10pJ), is measured via autocorrelation.

Analytical determination of the stop band tuning of photonic crystals infiltrated with liquid crystals

We demonstrate that the tuning of the optical properties of a photonic crystal infiltrated with liquid crystal can be calculate using the Von-Laue diffraction condition. We present a simple formula to predict the shift of the stop band for all the diffraction orders using an effective index of the composite structure. We consider that our formula is useful to determine in a simple manner the shift of the optical properties of tunable photonic crystals. We compare the accuracy of our method with calculations obtained with the Plane Wave Method.

Photonic Crystal Spectrometer

We demonstrate a new kind of optical spectrometer employing photonic crystal patterns to outcouple waveguided light from a transparent substrate. This spectrometer consists of an array of photonic crystal patterns, nanofabricated in a polymer on a glass substrate, combined with a camera. The camera captures an image of the light outcoupled from the patterned substrate; the array of patterns produces a spatially resolved map of intensities for different wavelength bands. The intensity map of the image is converted into a spectrum using the photonic crystal pattern response functions. We present…

Band structure of a two dimensional metallic photonic crystal and the experimental observation of negative refraction in the microwave region

In this paper we describe an application of the finite difference method to obtain the transverse magnetic photonic band gap diagram of a photonic crystal. The strategy of this method is to formulate the Maxwell equations in finite differences in order to write a computational code. We present experiments that confirm the validity of the calculations of the photonic band diagram as well as the refraction indix of such structure. All calculations were made for two dimensional metallic photonic crystal.

Modeling the optical properties of Twisted Bilayer Photonic Crystals

We demonstrate a photonic analog of twisted bilayer graphene that has ultra-flat photonic bands and exhibits extreme slow light behavior. Our twisted bilayer photonic device, which has an operating wavelength in C-band of the telecom window, uses two crystalline silicon photonic crystal slabs separated by a methyl methacrylate tunneling layer. We numerically determine the magic angle using a finite-element method and the corresponding photonic band structure, which exhibits a flat band over the entire Brillouin zone. This flat band causes the group velocity to approach zero and introduces ligh…

Signature of a three-dimensional photonic band gap observed on silicon inverse woodpile photonic crystals

We have studied the reflectivity of CMOS-compatible three-dimensional silicon inverse woodpile photonic crystals at near-infrared frequencies. Polarization-resolved reflectivity spectra were obtained from two orthogonal crystal surfaces corresponding to 1.88 pi sr solid angle. The spectra reveal broad peaks with high reflectivity up to 67 % that are independent of the spatial position on the crystals. The spectrally overlapping reflectivity peaks for all directions and polarizations form the signature of a broad photonic band gap with a relative bandwidth up to 16 %. This signature is supporte…

Guiding, bending, and splitting of coupled defect surface modes in a surface-wave photonic crystal

We experimentally demonstrate a type of waveguiding mechanism for coupled surface-wave defect modes in a surface-wave photonic crystal. Unlike conventional spoof surface plasmon waveguides, waveguiding of coupled surface-wave defect modes is achieved through weak coupling between tightly localized defect cavities in an otherwise gapped surface-wave photonic crystal, as a classical wave analogue of tight-binding electronic wavefunctions in solid state lattices.

Density of states governs light scattering in photonic crystals

We describe a smooth transition from (fully ordered) photonic crystal to (fully disordered) photonic glass that enables us to make an accurate measurement of the scattering mean free path in nanostructured media and, in turn, establishes the dominant role of the density of states. We have found one order of magnitude chromatic variation in the scattering mean free path in photonic crystals for just $\sim 3%$ shift around the band-gap ($\sim 27$ nm in wavelength).

非线性低对称光子晶体结构的自准直特性研究

Investigation of Self-Collimation Properties in Non-Linear Low Symmetry Photonic Crystal Structures

本研究针对由Kerr型非线性LiNbO3材料构成的低对称六角形光子晶体结构，提取其自准直特性并考察非线性折射率变化对传输特性的影响。

Two-dimensional coupled photonic crystal resonator arrays

We present the design and fabrication of photonic crystal structures exhibiting electromagnetic bands that are flattened in all crystal directions, i.e., whose frequency variation with wavevector is minimized. Such bands can be used to reduce group velocity of light propagating in arbitrary crystal direction, which is of importance for construction of miniaturized tunable optical delay components, low-threshold photonic crystal lasers, and study of nonlinear optics phenomena.

A New Demultiplexer Based Upon Two-Dimensional Photonic Crystals for OpticalIntegrated High-Density Circuits

A new conception of the wavelength division multiplexing on the basis of the two-dimensional photonic crystal was developed. The photonic crystals band structures were investigated in details. The method for the synthesis of the two-channel wavelength division multiplexer on the basis of two dimensional photonic crystals was developed using this method the device was synthesized. The spectral characteristics of the device and its dynamic pulse pattern response were investigated.